Electromagnetic switch for burglar-alarm systems



March 31. 1925. 1,531,302

C. B. MILES ELECTROMAGNETIC SWITCH FOR BURGLAR ALARM SYSTEMS Filed Sept. 21, 1923 Patented Mar. 31, 1925.

' UNITED STATES CHARLES B. MILES, OF TOLEDO, OHIO.

ELECTROMAGNETIC SWITCH FOR BURGLAR-ALARM SYSTEMS.

Application filed September 21, 1923.

Tod/Z w/w/nmay concern:

Be it known that I, Cir-units B. hTILES, a citizen of the United States, and a res1- dent of Toledo, 1n the county of Lucas and a htate of Ohio, have invented a new and useful Improvement 111 an Electromagnetic Switch for Burglar-Alarm Systems, which invention is fully set forth in the following specification.

My invention has for its object to provide an electro magnetic switch particularly adapted for-burglar alarm systems that will cause production of an alarm on the increase or on the decrease of the quantity of the current of the main line of the system. Thus the alarm will be operated if the circuit is served at any point or it will be operated if a source of supply of current is introduced by an outsider, such as, a burglar, with the the object of preventing the operation of the switch and consequently of the alarm.

The invention particularly has for its object to provide an electro magnetic switch for burglar alarm systems wherein a very low potential battery or cell may be used such as a dry cell for operating the system to control the switch and also to provide one wherein the circuit has very high resistance so that the current quantity is very small.

The invention may thus be contained in electro magnetic switches that vary in form. To illustrate a practical application of the invention I have showna switch containing my invention and a system in connection with which the switch may be used.

The figure illustrates diagrammatically a burglar alarm system and a switch operated thereby.

An electro magnet 1 is connected in the circuit to a battery 2 preferably a dry cell which has comparatively speaking low voltage. The resistance of the circuit of the battery and the magnet is relatively very high so that the current quantity is exceedingly small. The circuit is a closed circuit and the current flows continuously there thru at all times.

' A large part of the resistance of the circuit is preferably localized in one part of the circuit and so that when the resistance is short circuited, the cell 2 will produce a large current flow thru the magnet 1. The drawing illustrates diagrammatically two rooms in a building or two buildings that indicated by the squares 3 and 4. The circuit of the battery .2 passes thru the build- Serial No. 663,944.

ings 3 and -l. The connections in the building 3 preferably has a high resistance in series with the circuit. This may be in the form of protective burglar switches located in series, tin foil or other high resistance conductors located in walls or windows to be protected. The resistance is indicated by the resistance symbol 5. In the building =1 parallel lines are connected across the circuit of the cell 2. The circuit closers are connected to the parallel lines for completing the circuit of the cell 2 when any one ofthe circuit closers are operated. The circuit closers may be any contacting means used for protection against opening of windows and doors. hen any one of the circuit closers 6 is operated, the resistance of the circuit thru the building 3 is shunted which causes an increased flow of the current thru the magnet 1. If the circuit of the cell 2 is broken, a current thru the magnet 1 ceases to flow.

The armature of the magnet 1 is so constructed that it will complete an alarm circuit when the current thru the magnet is in creased or diminished above and below certain points. The armature 7 is pivotally supported on a pivoted arm 8. The armature 7 is pivotally connected to one end of the arm 8 while the arm 8 is pivotally supported at its other end. The armature 7 and the arm 8 are both located opposite the pole faces on the magnet. The armature 7 and the arm 8 is normally held by the magnet against one of its poles, the resistance of the circuit of the cell 2 being such as to normally prevent the other pole of the magnet from becoming sufliciently energized to bring the armature 7 in contact with its face. When therefore the current is increased in the main circuit the armature 7 is operated and also when the main circuit is broken the armature 7 and the arm 8 is moved from its magnet. This may be done by a suitable spring or it may be done by the weightof the armature and the arm.

Then the armature is moved either by reason of an increased or a decreased flow of current, a local alarm circuit is closed. Any simple alarm circuit may be used, such as the battery 10 and the electric bell 11. The alarm circuit is closed by means of a contact 12 that is connected to the armature '7 by the arm 13. The contact 12 may be a forked member that dips into a pair of mercury cups 14: that constitute the tenni nals of the alarm circuit so that when the armature and arm are allowed to' fall the alarm circuit may be closed. Also when the armature is raised, there is pivotally moved on the arm 8 by an increased flow of the current in the main line circuit, the arm 13 will lower the contact 12 into the mercury cups 14 and close the circuit.

I have thus provided an exceedingly simple burglar'system switch which Will sound an alarm it the wires are cut or if the circuit is opened by the circuit breaker orif a battery is connected across the circuit with the object of preventing operation of the alarm circuit when the main line circuit is cut or the circuit is broken at a point in the connection on the outside or where such an additional battery is connected to the circuit. i a

I claim: v

1. A circuit maker and breaker for alarm systems, comprising an electr'o-magnet, a pivot-allysupported arm, an armature pivotally supported on the arm, a movable contact operated by the armature and normally held open and closed when the current the arm and the armature are drawn to a pole of the magnet and closed when the current through the magnet increases sufiicientto cause the armature to be drawn to the other pole of the magnet or when the current through the magnet decreases in its thefirst named pole of the magnet.

In testimony whereof, I have hereunto signed my name to this specification.

CHARLES B. MILES.

flow suflicient to release the armature from 

